Molding for use in steel ingot making by bottom pouring and method of making steel ingot

ABSTRACT

An erupting flow of molten steel in the early stage of the bottom pouring method to make a steel ingot is interrupted by disposing at the bottom of an ingot-making mold a molding which comprises about 40 to 96 percent by weight of a refractory material, 2 to about 50 percent by weight of a fibrous material and 2 to about 20 percent by weight of a binder. The molding has a size such that it is larger than the steel run-out hole in mold and can rise and float on the top surface of the molten steel within the mold. Thus, splashing can be prevented and a smooth casting surface can be obtained. The molding and the process are disclosed.

United States Patent [1 1 1111 3,810,506

Kobayashi May 14, 1974 1 MOLDING FOR USE IN STEEL INGOT 3.182,363 5/1965 Ferree 164/133 MAKING BY BOTTOM POURING AND 316231537 "/1971 METHOD OF MAKING STEEL INGOT Hidetaka Kobayashi, Hasuda, Japan Aikoh Co., Ltd.. Tokyo. Japan Dec. 4, 1972 lnventorz.

Assignee:

Filed:

Appl. No.:

Foreign Application Priority Data Dec. 4, 1971 Japan 46-97591 US. Cl 164/133, 249/109, 249/110 Int. Cl: B22121 1/00, B22d 23/00 Field of Search 164/133; 249/109, 110,

References Cited UNITED STATES PATENTS Hilton et al .L 164/133 Primary EmminerCharles W. Lanham Assistant Examiner-Victor A. DiPalma Attorney. Agent. or Firn1-Sughrue. Rothwell. Mion, Zinn & Macpeak [57] ABSTRACT An erupting flow of molten steel in the early stage of 1 ing can be prevented and a smooth casting surface can be obtained. The molding and the process are disclosed.

15 Claims, 3 Drawing Figures MOLDING FOR USE IN STEEL INGOT MAKING BY BOTTOM POURING ANDMETI-IOD OF MAKING STEEL INGOT BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to a molding for interrupting an erupting stream of molten steel which occurs in the early pouring stage in the manufacture of steel ingot by the bottom pouring method, and to a method of making steel ingot by bottom pouring using such molding.

2. Description of the Prior Art In the manufacture of steel ingot by the bottom pouring'method, molten steel is poured from a ladle into a pouring tube, passed through a runner and then poured into a mold from a run-outhole. In the early stage of the bottom pouring method the molten steel abruptly erupts from the run-out hole into the mold as an erupting stream of molten steel because pouring is performed abruptly so as to avoid blockage of the runner due to solidification of the molten steel upon cooling and no molten steel is present within the mold which prevents or reduces the eruption of the molten steel. Further, the difference in height between the pouring tube and the bottom of the mold alsocontributes to the force of the erupting molten steel. A great deal of splashing occurs as a result of the formation of the erupting stream, and steel adheres to the bottom of the mold in the solidified state which deteriorates the cast ing surface of the bottom of the steel ingot produced. Such a poor casting surface must be removed by a separate peeling step which results in a reduction in work- SUMMARY OF THE INVENTION According to the present invention, there is provided a molding for use in-making steel ingot by the bottom pouring method, the molding comprising about 40 to 96 percent by weight of a refractory material, 2 to about 50 percent by weight of a fibrous material and 2 to about pegcent by weight of a binder tinihaving a size such that it is larger than the diameter of the runout hole for the introduction of molten steel into the mold and can rise and float on the top surface of the molten steel within the mold, the molding being disposed at the bottom of the mold to interrupt the erupting stream of molten steel during the early stage of pouring.

All percentages in the molding are based on the total weight of the molding in the above descussion.

The present invention also provides a method of making steel ingot by bottom pouring using the abovedescribed molding, whereby an erupting stream of molten steel is interrupted to prevent splashing and to smoothen the casting surface of the bottom of the resulting steel ingot and, at the same time, the molten steel is prevented from directly striking the wall of the mold even when it erupts obliquely.

It is thus one object of the present invention to provide an improved process for making steel ingot by the bottom pouring method.

It is further object of the present invention to provide an improved process for making steel ingot by the bottom pouring method wherein splashing is prevented and the casting surface of the bottom of the resulting steel ingot is smoothened.

A further object of the invention is to provide a molding for use in the bottom pouring method which enables theheretofore recited objects to .be met.

These and other objects of the present invention will become clearer from the following description of the invention when read in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic vertical sectional view of steel ingot making apparatus which shows the initial stage of pouring in the manufacture of steel ingot by the bottom pouring method, the right-hand side view showing a this invention.

DETAILED DESCRIPTION OF THE INVENTION The refractory material used in the present invention may be any refractory material able to withstand the temperature of the molten steel, and specific examples thereof include inorganic materials such as olivine, quartz, silica sand, refractory silicate, magnesia, alumina, mullite, slag, aluminum ash, diatomaceous earth,

vermiculite, shale, obsidian, pearlite rock, magnesite,.

limestone, dolomite, fly ash, and bauxite. Alundum can also be used.

The proportion of the refractory material is about 40 i to 96 percent by weight of the weight of the molding. If it is less than about 40 percent by weight, the refractory property (ability to withstand heat) and the strength of the molding are reduced. The use of an amount of refractory material in excess of 96 percent by weight is undesirable because insufficient fibrous material and binder will be present to maintain the strength of the molding which is used for interrupting the erupting stream of molten steel.

The fibrous material is used .to reinforce the molding so that it will not be broken by the impact of the erupting molten steel. Examples of fibrous materials that can be used in this invention are wood pulp, wood sawdust, beaten waste paper, cotton, asbestos, slag wool, rock wool, glass wool, steel wool, and artificial fibers, e.g., rayon. The proportion of the fibrous material is 2 to about 50 percent by weight of the weight of the molding. If the proportion thereof is less than 2 percent by weight, the amount of fibrous material is insufficient to reinforce the molding. It is not necessary to use the fibrous material in an amount exceeding about 50 percent by weight, usually it is not necessary to use more than about 40 percent by weight of fibrous material, but up to about 50 percent by weight may be used, in which case the amount of binder is reduced to 10 if 40 percent by weight of refractory material is used.

The binder used may, for example, be a resin such as a phenol-formaldehyde resin, urea-formaldehyde resin, furan resin or epoxy resin, water glass, cements, clays,

dextrin, or starch. The proportion of the binder is 2 to about percent by weight of the weight of the molding. if the proportion thereof is less than 2 percentby weight, the binder has insufficient effect in binding the component elements of the molding and the molding tends to be disintegrated, making it difficult to handle. No significant increased effect is obtained by using the binder inan amount larger than about 20 percent by weight.

The molding of this invention is used in the same operation and brings about the same results as conventional casting surface improving agents such as a platelike or powdery material for coating the top surface of molten steel, and can prevent the formation of an oxide coating of the top surface of molten steel rising within the mold as a result of contact of the steel with air or a crust forming as a result of air cooling.

It is possible to include in the molding of the present invention a substance capable of generating a. reducing atmosphere which excludes the atmosphere, such as fluorides, chlorides and carbonaceous substances as are well known in the art, for example, fluorides such as sodium hexafluoroaluminate, sodium hexafluorosilicate, potassium hexafluorosilicate, calcium hexafluorosilicate, sodium borofluoride, potassium boro-' fluoride and aluminum fluoride; chlorides such as aluminum chloride, chlorinated paraffins and hexachloroethane; and carbonaceous materials such as various cokes, charcoal, coal and carbon black. If desired, in order that any portion of the molding which comes in contact with the molten steel will be melted and remove non metal foreign matters in the molten steelto thereby increase the purity of the steel, a slag-forming agent such as limestone or calcium fluoride or a meltin g point regulating agent such as cryolite, sodium fluoride or chloride, potassium fluoride or chloride, manganese oxide, sodium carbonate or potassium carbonate may also be included in the molding. These materials are usually added in low proportions, e.g., less than about lO percent by weight of the three essential components of the molding. The addition of such material does not effect the percentage basis of the three essential components.

The molding of this invention does not have to be of the same configuration as the cross sectional shape of the inner surface of the mold so long as it has 'a size such that it is larger than the diameter of the run-out hole for the introduction of molten steel into the mold and can rise and float on the top surface of molten steel within the mold.

The molding can produced by any. known process. For example, it can be producedby forming an aqueous slurry of the components and drying the same or by any equivalent process.

Most preferably, the molding has a density of about 0.5 to about 1.5 g/cc. This bulk density is best suited to most commercially used bottom pouring methods. A preferred density is 0.6 1.0 g/cc.

The thickness of the molding is not overly critical, and it is only necessary the molding have sufficient thickness so it can be easily handled, is not cracked by the erupting molten steel stream or is not tipped over if a relatively small molding is used. Usually, however, since a molding of relatively large diameter is used the main criterion which establishes thickness is that the molding be easily handled and not so thin as to break when the molten steel stream initially hits it.

The method of making steel ingot by bottom pouring in accordance with the present invention will now be described with reference to the accompanying drawings and'compared to a conventional bottom pouring method, and two embodiments of the molding of this invention will be described in greater detail.

With reference to FIG. 1, in steel ingot making by bottom pouring molten steel 6 is poured into a pouring tube 3 from a ladle (not shown), passes. through a runner 4 in a bottom pouring bed 2, and is then poured into a mold 1 from a run-out hole 5. In the conventional steel ingot making shown on the right-hand side of F l0. 1 the molten steel erupts from the run-out hole 5,,and the erupting molten steel stream 7 which is formed rises in the interior of the mold, resulting in a great deal of splashes scattering towards the wall of the mold. The casting surface of the bottom of the steel ingot made by this conventional method becomes poor, and must be peeled. On the left-hand side, a molded article 8 in accordance with this invention is disposed at the bottom of the mold l to interrupt the erupting flow of molten steel which is formed in the early stage of pouring, and the occurrence of splashes is greatly reduced, as shown. The bottom of the steel ingot made by this method has a very smooth casting surface, and a peeling step is hardly necessary.

The moldingcan be circular as shown in FIG. 2 or rectangular and box-like shape as shown in FIG. 3. Needless to say, one skilled in the art will appreciate other shapes are also acceptable.

One specific example of steel ingot making in accordance with this invention will be given below together with a comparison example.

The molding was prepared as follows.

A slurry was prepared by. homogeneously mixing 40 percent by weight of the above composition with 60 percent by weight of water. The slurry was charged. into a metallic mold which was provided with a wire net in such an amount that the charged slurry decreased to about 20 mm in thickness when it was dehydrated through the wire net by vacuum. The dehydrated molding was dried at a temperature of to C for 2 hours to obtain a discoid molding 20 mm thick and 400 mm in diameter.

A pouring tube was mounted at the centre of a bottom pouring bed, and 6 molds for making a 5-ton steel ingot were arranged radially therearound. Six steel ingots were made with one bottom casting. Three of the six steel ingots were made using molds with the de scribed discoid molding at the bottom. The other three steel ingots were produced using a conventional powdery casting surface improving agent, mainly composed of fly ash, a fluoride, carbonate etc.

Composition of the molding Siliceous sand 30% by weight refractory Diatomaceous earth 40% by weight Sodium fluoride 8% by weight melting point regulating agent Beaten waste paper fibrous matl Phenolformaldehy de resin 17% by weight ever, with the three ingots made by the conventional ingot making process the casting surface at the bottom of the steel ingot was poor because of a great deal of splashing caused by the eruption of the molten steel. It

was necessary to peel the poor casting surface before rolling the ingot. As a result of peeling, the average yield of the steel ingot decreased to 94.8 percent (same basis as above).

While the invention has been described in detail and with reference to specific embodiments thereof, it will be apparent to one skilled in the art that various changes and modifications can be made therein without departing from the spirit and scope thereof.

What is claimed is:

l. A molding for making steel ingot by the bottom pouring method, said molding being set at the bottom of the mold in which bottom pouring is conducted to interrupt a spouting stream of molten bottom steel issuing from a run-out hole in the bottom of the mold during pouring, said molding comprising about 40 to 96 percent by weight of a refractory material, 2 to about 50 percent by weight of a fibrous material and 2 to about percent by weight of a binder and having a size such that it is larger than the diameter of the runout hole to permit entry of the molten steel into the mold and can rise and float on the top surface of the molten steel within the mold.

2. The molding of claim 1 which further includes a material capable of generating a gas during bottom pouring to form a reducing atmosphere which prevents the atmosphere from contacting the molten steel.

3. The molding of claim 2 wherein said material is selected from the group consisting of fluorides, chlorides and carbonaceous substances.

4. The molding of claim 1 which slag-forming agent.

5. The molding of claim 1 whichfurther includes a melting point controlling agent.

6. The melding of claim 4 wherein said slag-forming agent is selected from the group consisting of limestone and calcium fluoride.

7. The molding of claim 5 wherein the melting point controlling agent is selected-from the group consisting of cryolite, sodium fluoride or chlorideljpotassium fluoride or chloride, manganese oxide, so ium carbonate and potassium carbonate.

further includes a 8. The molding of claim 1 wherein the refractory material is selected from the group consisting of olivine, quartz, silica sand, a refractory silicate, magnesia, alumina, mullite, slag, aluminum ash, diatomaceous earth, vermiculite, shale, obsidian, pearlite, magnesite, limestone, dolomite, fly ash and bauxite.

9. The molding of claim 1 wherein the fibrous material is selected from the group consisting of wood pulp, wood sawdust, beaten waste paper, cotton, asbestos, slag wool, rock wool, glass wool, steel wool and artificial fibers.

10. The molding of claim 1 wherein the binder is selected from the group consisting of resins, water glass, cements, clays, dextrin and starch,

11. The molding of claim 10 wherein the resin is selected from the group consisting of a phenolformaldehyde resin, urea-formaldehyde resin, furan resin and epoxy resin.

12. In a method of making steel ingot by the bottom pouring method, the improvement wherein a molding comprising from about 40 to 96 percent by weight of a refractory material, from 2 to about 50 percent by weight of a fibrous material and from 2 to about 20 percent by weight of a binder and having a size such that it is larger than the diameter of the run-out hole in the mold for the introduction of molten steel into the mold andcan' rise and float on the top surface of molten steel within the mold is provided at the bottom of the mold to thereby interrupt an erupting stream of molten steel during pouring.

13. The method of claim 12 wherein the refractory material is selected from the group consisting of olivine, quartz, silica sand, at refractory silicate, magnesia, alumina, mullite, slag, aluminum ash, diatomaceous earth, vermiculite, shale, obsidian, pearlite magnesite, limestone, dolomite, fly ash and bauxite.

14. The method of claim 12 wherein the fibrous material is selected from the group consisting of wool pulp, wood sawdust, beaten waste paper, cotton, asbestos, slag wool, rock wool, glass wool, steel wool and artificial fibers.

15. The method of claim 12 wherein the binder is selected from the group consisting of resins, water glass,

cements, clays, dextrin and starch. 

2. The molding of claim 1 which further includes a material capable of generating a gas during bottom pouring to form a reducing atmosphere which prevents the atmosphere from contacting the molten steel.
 3. The molding of claim 2 wherein said material is selected from the group consisting of fluorides, chlorides and carbonaceous substances.
 4. The molding of claim 1 which further includes a slag-forming agent.
 5. The molding of claim 1 which further includes a melting point controlling agent.
 6. The molding of claim 4 wherein said slag-forming agent is selected from the group consisting of limestone and calcium fluoride.
 7. The molding of claim 5 wherein the melting point controlling agent is selected from the group consisting of cryolite, sodium fluoride or chloride, potassium fluoride or chloride, manganese oxide, sodium carbonate and potassium carbonate.
 8. The molding of claim 1 wherein the refractory material is selected from the group consisting of olivine, quartz, silica sand, a refractory silicate, magnesia, alumina, mullite, slag, aluminum ash, diatomaceous earth, vermiculite, shale, obsidian, pearlite, magnesite, limestone, dolomite, fly ash and bauxite.
 9. The molding of claim 1 wherein the fibrous material is selected from the group consisting of wood pulp, wood sawdust, beaten waste paper, cotton, asbestos, slag wool, rock wool, glass wool, steel wool and artificial fibers.
 10. The molding of claim 1 wherein the binder is selected from the group consisting of resins, water glass, cements, clays, dextrin and starch.
 11. The molding of claim 10 wherein the resin is selected from the group consisting of a phenol-formaldehyde resin, urea-formaldehyde resin, furan resin and epoxy resin.
 12. In a method of making steel ingot by the bottom pouring method, the improvement wherein a molding comprising from about 40 to 96 percent by weight of a refractory material, from 2 to about 50 percent by weight of a fibrous material and from 2 to about 20 percent by weight of a binder and having a size such that it is larger than the diameter of the run-out hole in the mold for the introduction of molten steel into the mold and can rise and float on the top surface of molten steel within the mold is provided at the bottom of the mold to thereby interrupt an erupting stream of molten steel during pouring.
 13. The method of claim 12 wherein the refractory material is selected from the group consisting of olivine, quartz, silica sand, a refractory silicate, magnesia, alumina, mullite, slag, aluminum ash, diatomaceous earth, vermiculite, shale, obsidian, pearlite magnesite, limestone, dolomite, fly ash and bauxite.
 14. The method of claim 12 wherein the fibrous material is selected from the group consisting of wool pulp, wood sawdust, beaten waste paper, cotton, asbestos, slag wool, rock wool, glass wool, steel wool and artificial fibers.
 15. The method of claim 12 wherein the binder is selected from the group consisting of resins, water glass, cements, clays, dextrin and starch. 